What Is DCE RPC?
DCE RPC is a facility for calling a procedure on a remote machine as if it were a local procedure call. To the application programmer, a remote call looks (almost) like a local call, but there are several RPC components that work together to implement this facility, including the Interface Definition Language (IDL) and its compiler, a Universal Unique Identifier (UUID) generator, and the RPC runtime, which supports two RPC protocol implementations. One RPC protocol operates over connection-oriented transports such as the Transmission Control Protocol/Internet Protocol (TCP/IP) and the other RPC protocol operates over connectionless transports such as the User Datagram Protocol/Internet Protocol (UDP/IP).
An end user does not see RPC at all, and the minimal amount of administration involved in RPC can usually be handled by the server-side application code, such as advertising an application server in the DCE Directory Service. It is the application programmer who most comes into contact with the RPC component. Since many of the DCE components are themselves client/server applications, they use RPC as their basis for distributed communications.
The components that comprise the DCE RPC are as follows:
· The Interface Definition Language (IDL) and its compiler
An RPC interface is described in DCE IDL. The IDL file is compiled into object code using the IDL compiler. The object code is in two main parts - one for the client side of the application, and one for the server side.
· The RPC runtime library
This library consists of a set of routines, linked with both the client and server sides of an application, which implement the communications between them. This involves the client finding the server in the distributed system, getting messages back and forth, managing any state that exists between requests, and processing any errors that occur.
· Authenticated RPC
DCE RPC is integrated with the DCE Security Service component to provide secure communications. Levels of security can be controlled by the RPC application programmer through the authenticated RPC API. (See Programming with DCE Security for more information on Authenticated RPC.)
· Name Service Independent (NSI) API
DCE RPC is integrated with the DCE Directory Service component to facilitate the location of RPC-based servers by their clients. The NSI routines allow a programmer to control the association, or binding, of a client to a server during RPC.
· The DCE host daemon
The DCE host daemon (dced) is a program that runs on every DCE machine. It includes (among other things) an RPC-specific name server called the endpoint mapper service, which manages a database that maps RPC servers to the transport endpoints (in IP, the ports) that the server is listening for requests on.
· The DCE control program
The DCE control program (dcecp) is a tool for administering DCE.
· UUID facilities
These are ancillary commands and routines for generating Universal Unique Identifiers (UUIDs), which uniquely identify an RPC interface or any other resource. The uuidgen program can optionally generate an IDL template for a service interface, along with a unique identifier for the interface.